Adjunct Based Services (ABS) are services introduced on an Adjunct based architecture containing adjunct processors. An adjunct is a well known component of the Advanced Intelligent Network (AIN) Architecture. In this document, the term "Adjunct" is consistent with common usage and generally refers to a system connected to a switching system that may provide, for example, service logic, DTMF detection, and announcements. As such, the term "Adjunct" here may include the AIN Adjunct functionality and Intelligent Peripheral Functionality and the International Telecommunications Union (ITU) Services Node functionality as would be understood by a person skilled in the art. Services are typically deployed on an Adjunct based architecture to meet cost or time-to-market requirements that cannot be achieved by other architectures (for example, switch based architectures). Numerous ABS have been offered in both the consumer and business markets. An example of an ABS is the 800 Transfer Connect Service (TCS).
800 Transfer Connect Service(TCS) is an automated call routing service provided by long distance carriers for certain customers utilizing 1-800 numbers. In general, TCS provides post answer call redirection features to a caller, for example, conferencing, consultation, blind transfer, etc. Such services are invaluable to the holders of the 800 numbers, for example large corporations, in that customer calls may be directed to any one of a number of corporate locations in an extremely efficient manner. Specifically, TCS allows the called party to redirect calls to an 800 number, POTS (plain old telephone service) number, or a predefined speed dial code.
Prior art TCS systems utilized a small scale adjunct (SSA) architecture to route a specified set of customer traffic to a primary adjunct site. Each Adjunct site is assigned a Special Service Code (SSC) which is used for routing purposes; that is, there is a one-to-one relationship between SSC and adjunct site. Routing tables provide routing to a primary adjunct site and overflow sites. The routing tables, referred to as multiple routing treatment (MRT) tables, are located at the originating switch (OAS) of the long distance carrier to route calls to a specified adjunct site. Each customer to TCS is assigned an Adjunct Routing Number (ARN) in the format SSC-AAA-XXXX. Each Adjunct site is engineered to handle the capacity of a specified set of customers.
Referring to FIG. 1, there is shown an exemplary call flow for an ABS 10 utilized in the prior art. The ABS call flow is a key aspect of the ABS architecture; further aspects of the Adjunct Based Architecture will be discussed herein. As shown in FIG. 1, a caller dials a 1800-NXX-XXXX toll free call and the call is sent by the Local Exchange Carrier (LEC) 12. The LEC performs 10-digit translation of the dialed 800 toll free number to determine the appropriate telecommunications network. The LEC then passes the call to the originating switch (OAS) 14 of the appropriate telecommunications network. As would be understood, switches, such as the OAS, provide connection control for network calls in a well-known manner. Based on digit translation of the dialed 800 toll free number, the OAS signals a customer database 16 with the dialed 800 toll free number and the Automatic Number Identifier (ANI) of the caller. The database retrieves and executes the customer record. The database returns an ARN in the format SSC-AAA-XXXX to the OAS 14. Based on 3-digit translation of the ARN (SSC) at the OAS 14, the OAS points the call to the appropriate MRT Table 17, which resides in the switch, for example.
The MRT Table 17 provides routing instructions to a primary adjunct site 19 and the overflow sites. As shown in FIG. 1, the MRT Table provides the routing instructions for the switch to route the call to the primary Adjunct site 19. The MRT Table provides the Call Type equal to Destination Switch Number and the Network Switch Number NRN) equal to 094. The OAS routes the call to the terminating switch (TAS) A 18 based on the MRT Table information. The TAS A 18 translates the first 3-digits of the ARN (SSC) and points the call to another MRT Table. The MRT Table (TAS A) 15 provides the Call Type equal to Routing Data Block and the Call Data equal to 261. The MRT Table routes the call to the primary Adjunct site based on the MRT Table information. The first route chosen is the trunk sub-group to the adjunct site. If the trunk sub-group fails/busy or the primary adjunct site 19 is down, the call is cranked back to the OAS and the OAS points the call back to the MRT Table 17. The OAS then routes the call to the second route choice which provides routing instructions to the overflow adjunct site.
Referring to FIG. 2, there is shown an exemplary "partial" network architecture 20 based on the previously described TCS call flow 10. This figure effectively illustrates some key disadvantages of the prior art. Specific disadvantages include: cost effectiveness, OAS to TAS A focusing leading to intertoll blocking, TAS A to TAS B focusing leading to intertoll blocking, architecture instability under fluctuations of traffic loads, and customer perceived reliability; each of these points are considered in turn.
It is well known in traffic theory that large trunk groups more efficiently handle traffic than small trunk groups (Erlang-B distribution). The prior art ABS architecture routes all originating traffic from any OAS 14 in the network to a single TAS A 18. This routing is artificial in that large volumes of traffic flow between switches that normally support minimal traffic (e.g., the community of interest between Iowa and New York is much less than between New York and Philadelphia). As a result large amounts of traffic flow along pathways with few trunks 11. This results in large numbers of calls requiring via routing (potentially blocked); via routed calls increase Post Dial Delay and require more network resources. A similar phenomena holds for the TAS A to TAS B leg of the call. For large customers, who access the network from a TAS B geographically removed from TAS A, there will be large amounts of traffic focused on small intertoll trunk groups. The OAS-TAS A and TAS A-TAS B focusing effects result in extra cost and poor performance.
The prior art architecture is also not stable under reasonable fluctuations of customer traffic (fluctuations particularly prevalent for 800 ABS). Consider an adjunct engineered to a load of X utilization of which a large customer uses wX of the capacity. Note that wX is the total network load for the customer and that it is not uncommon for w to have a value of 0.5 or greater. If, as a result of media stimulated calling by that particular customer, the load increases to double the normal load, the adjunct would be in severe congestion (150% load). This would most likely result in network congestion, intertoll blocking and lost calls. Similarly, if a given adjunct site fails (especially in the case of a failure that evades automatic detection) all of a given customers traffic is affected.
Another disadvantage of the prior art is that for each adjunct deployed in the network a new SSC code is required. There are a finite number of SSC codes available; further growth of the prior art architecture would lead to exhaustion of these codes. Accordingly, there is a need for a more flexible network architecture that effectively supports ABS traffic.